Almost all residents of Indonesia's most populous island of Java have antibodies against Covid-19, owing to a combination of prior infection and vaccination against the virus, a government-commissioned survey showed.
The March study of 2,100 people, conducted on Java, home to 150 million people, and Bali, Indonesia's top tourism destination, revealed 99.2% of people had Covid antibodies, a 6 percentage point increase from a December survey.
Pandu Riono, an epidemiologist at the University of Indonesia, which conducted the survey with the health ministry, on Monday told Reuters the antibody levels in the latest survey were higher due to a wider booster shot rollout, as recipients had stronger protection.
Indonesia's daily case numbers have decreased significantly since a spike in February driven by the Omicron variant. About 60% of its 270 million people have been vaccinated against Covid.
Pandu said the stronger antibodies may explain the faster rate at which Omicron variant infections declined in Indonesia.
The December study, of 22,000 people, was conducted nationwide and showed 86% of Indonesians had antibodies.
The world's largest Muslim-majority nation has recently loosened many of its pandemic restrictions, including waiving quarantine for foreign tourists and lifting a two-year ban on the mass exodus tradition during the Muslim holiday season of Eid al-Fitr.
Health minister Budi Gunadi Sadikin on Monday said the survey was a factor in the government's assessment that the holiday "can go smoothly without bringing negative impacts on our people".
The study closely tracks recent data in Britain, where the percentage of adults with Covid antibodies in the middle of March was nearly 99%, according to its Office for National Statistics.